The present invention relates to a semiconductor device comprising MOS (Metal Oxide Semiconductor) transistors and a method for fabricating the semiconductor device, more specifically, a semiconductor device subjected to hydrogen annealing for recovering damages caused in the fabrication steps, and a method for fabricating the semiconductor device.
Conventionally, hydrogen annealing is performed for recovering damages by etching, etc. is made on MOS transistors. Such hydrogen annealing is made under conditions of, e.g., an atmosphere containing hydrogen and nitrogen, a 5–20% hydrogen concentration, a 350–450° C. temperature and 10–130 minutes (refer to Japanese Patent Application Unexamined Publication No. Hei 7-74167 (1995)).
Furthermore, for the hydrogen annealing for recovering the step damages is also proposed a method for fabricating a semiconductor device in which for making the damage recovery sufficient even in the presence of interconnection layers containing titanium layers, the hydrogen concentration of the annealing atmosphere is set in consideration of the hydrogen occluded amounts of the titanium layers (refer to Japanese Patent Application Unexamined Publication No. Hei 9-252131 (1997)).
High relative accuracy is required of the MOS transistors of semiconductor integrated circuits. Such integrated circuits are, e.g., differential circuit unit of operational amplifiers and comparators, differential circuits used in the comparators of successive A/D converters, pipeline A/D converters, etc., current mirror circuits used in the current mirror units of current output D/A converters, and others. These semiconductor integrated circuits are used in various electrical apparatus and communication systems; they are used, e.g., in the operational amplifiers of cellular phones, modems, etc., the successive A/D converters of digital cameras, video cameras, sensors, etc., the pipeline A/D converters of wireless LANs, FWAs (Fixed Wireless Accesses), digital TVs, etc., and the current output D/A converters of TVs, VTRs, digital cameras, video cameras, wireless LANs, FWAs, etc.